Manufacture of iron and steel alloys



Patented May 26, 1925.

UNITED STATES 1,538,893 PATENT OFFICE:

WALTER BIBKETT HAMILTON, O F BIRKDALE, AND THOMAS ALLEN EVANS, OF

MANCHESTER, ENGLAND.

nanornc'rurm or 13011 AND STEEL ALLOYS.

No Drawing.

To all whom it may concern:

Be 1t known that we, WALTER BIRKETT HAMIL'roN, of Birkdale, in thecounty of,

Lancaster, England, and THOMAS ALIEN EvANs, of Cheetham Hill,Manchester, in the.

county of Lancaster, England, both subjects of the King of GreatBritain, have invented new and useful Improvements in the Manufacture ofIron and Steel Alloys, of which the following is a specification.

The present invention has reference to improvements in the manufactureof iron and steel alloys. In the specification of Letters Patent No.1,432,289 granted to us. there is described a process for themanufacture of such alloys in which a mixture of aluminum and ordinarycommercial chrome ore is employed.

In the practice of such process it is (16-. sirable to use a certainexcess of the thermo reducing agent beyond the quantity theoreticallyrequired to reduce the reducible metallic oxides contained in the ore.This 1 This is detrimental to the quality of the metal, at-any rate formany of its uses.

We will suppose that it is found that sufficient silicon has beenreduced to render the percentage content of that element in the alloyproduced as high, for example, as 3%. If the aluminum were able toselectively reduce only the reducible metallic oxides, then by leavingout the chemically equivalent amount of aluminum necessary for thereduction of such a quantity of silicon such siliconwould no longer befound in the alloy produced.

In practice it is found that so diminishing the quantity of aluminumdoes not entirely prevent silicon being found in the alloy producedandfurther that the percentage of chromium in the alloy is diminished.

The object of .he' present invention is to provide a process wherebyores containing Application flled November 2, 1923. Serial No. 672,274.

substantial proportions of silica can be employed and the ultimateproduct contain the desired amount of chromium without silicon inundesirable quantities.

A further 0b]60t of the present invention is that the process shall becapable of being carried out by ordinary steel works hands with theconsistent production of metal that will conform to the desiredspecification.

'According to our present invention we employ a quantity of aluminum inexcess of the quantity chemically equivalent to the reducible metallicoxides in the ore but ,we intimately mix with it not the whole quantityof the chromite but approximately only 80% thereof, the remainingchromite being kept separate from the mixture and used in the followingmanner This 20% or thereabouts of the chromite is added to a suitablereception slag (which as described in the aforesaid patent may be asilicious lime slag) .which is brought to a highly fluid conditionbefore adding the mixture containing the or thereabouts of the chromiteand all the aluminum.

The reception slag accordingly-contains a known proportion of chromiumoxide. These percentages 20 and 80 are subject to considerablevariations with different chrome ores. The aluminum is in such quantitythat it will be sufficient to reduce practically all,

if not all, the reducible oxides, including the silica, contained insuch portion of the chromite as is admixed with-the aluminum. Theportion of the chromite added to the reception slag and with which noaluminum is previously mixed should .be sufiicienttoutilize the'siliconproduced by reduction of the silica content of that portion of thechromite with which the aluminum is admixed.

The silicon .reduced from the silica expends itself in reducing theoxide of chromium added to the reception slag. The proc- 'ess is carriedout preferably in an electric furnace. The furnace is charged with asuit-- able metal, viz, iron or steel, which may be molten bath ofmetalfrom contamination by the electrodes.

Our present invention is not limited to the case where the reducingagent added to the chrome ore is aluminum, as We have usefully appliedour invention to the case where aluminum mixed with silicon has been thereducing agent.

Further, if desired instead of mixin the reducing agent and such portion0 the chrome ore as we have described as being mixed therewith, we maycharge the same separately and .in any order-but we prefer to charge thesame in intimate admixture. Although it is contemplated that the sameore will be used both for adding to the reception slag and for admixingWith the thermo reducing agent and that this will contain silica insubstantial proportions, it should be observed that it is not necessarythat the ore added to the slag should con-. tain the same percentage ofsilica as that contained in the ore admixed with the thermo-reducingagent, or any silica.

What we claim as our invention and desire to secure by Letters Patent isv 1. A process of making an alloy containing iron andchromium,'consisting in charge ing a furnace with suitable metal,forming a reception slag which carries an ore containing chromium andiron oxides, adding to the furnace an ore containing chromium and ironoxides and substantial proportions of silica admixed with a sufficientquantity of a reducing agent exothermic in respect to said oxides toreduce substantially all the reducible oxides including the silica,contained in the ore so added, whereby the silicon reduced from thesilica expends itself in reducing the chromium oxide contained in thereception slag, thereby to produce an alloy containing the desiredpercentages of iron and chromium and substantially free from silicon,substantially as described 2. A process of making an alloy containingiron and chromium which consists in charging a furnace with suitablemetal, forming a reception slag with which an ore containing chromiumand iron oxides is mixed, charging into the furnace further quantitiesof such an ore and a reducing agent exothermic in respect to saidoxides, the quantities of the ore mixed with the slag and charged intothe furnace, respectively and of the reducing agent, being all soproportioned that the silicon reduced in said further charge expendsitself in reducing the chromium oxide contained in the reception slag,whereby an alloy of the desired percentages of iron and chromium andsubstantially free from silicon is obtained, substantially as described.V

3. A process of making an alloy containing iron and chromium, whichconsists in charging a furnace with suitable metal, forming a receptionslag containing chromium and iron oxides, addin to the furnace an orecontaining chromium and iron oxides and a reducing agent exothermic inrespect to said oxides, the percentages of chromium contained in theslag to that contained in the mixture with the reducing agent beingapproximately 1 to 4, whereby the silicon reduced by the reducing agentexpends itself in reducing the chromium contained in the reception slag.

4. A process of making an alloy containing iron and chromium, whichconsists in charging a furnace with suitable metal, forming a slagcontaining approximately 20% of the total quantity of chromium to beadded, bringing said slag to a highly fluid condition, and addingthereto a mixture containing approximately of said total quantity ofchromium with iron oxides and a reducing agent exothermic in respect tosaid oxides, whereby the silicon reduced by the reducingagent expendsitself in reducing the chromium'contained in the reception slag.

In testimony whereof we have signed our names to this specification.

WALTER BIRKETT HAMILTON. THOMAS ALLEN EVANS.

